Cut the tomato in slices, then cut each slice into smaller pieces. Put half the chopped tomato (including seeds and juice) in each beaker. Mash the tomato pieces with a spoon to make a pulpy mixture.
Insert a copper and zinc electrode into each beaker, making sure that they do not touch. You have now made two battery cells! Set one beaker aside for the moment.
In the remaining beaker, clip one wire lead to the zinc electrode and another to the copper electrode.
Hold the headphones near your ears, then touch the loose ends of the wire leads to the metal end of the headphone cord. If you look closely at the headphone plug, there will be several sections. Try touching the wires to different sections until you can hear the crackle of electricity that is being produced by your tomato battery cell.